51V NMR and EPR study of the mechanistic details of oxidation with VO(O2) (Pic) (H2O)2

Q4 Chemical Engineering

分子催化 Pub Date : 1994-09-13 DOI:10.1016/0304-5102(94)00069-7

E.P. Talsi , K.V. Shalyaev

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引用次数: 18

Abstract

Using ⁵¹V NMR, it was shown that peroxo complex VO(O₂) (Pic) (H₂O)₂ (Pic = picolinic acid) exists in CH₃CN, MeOH and H₂O in the forms of VO(O₂) (Pic) H₂O·CH₃CN, VO(O₂) (Pic) H₂O·MeOH and VO(O₂) (Pic) (H₂O)₂, respectively. To elucidate the nature of reactivity of vanadium peroxo complexes Of VO(O₂) (Pic) H₂O·S family towards hydrocarbons their interactions with spin trap 3,3,5,5-tetramethyl-pyrroline-N-oxide (TMPO) were investigated by EPR. Only the peroxo complex VO(O₂) (Pic) H₂O·CH₃CN was reactive towards the hydrocarbons and the spin trap. This complex can abstract the β-hydrogen atom from TMPO (V^V reduces to V^IV by this reaction). Such hydrogen atom abstraction was not observed for the other radical species studied (free radicals OH•(HO₂•), RO•(RO₂•) and superoxo complex Pd₃(OAc)₅O₂•). The latter species form with TMPO a spin adduct by addition to the double bond. The data provide evidence, that the diradical species V^IVOO• are active particles of oxidation by VO(O₂) (Pic) H₂O·CH₃CN.

Deactivation of VO(O₂) (Pic) H₂O·CH₃CN upon substitution of CH₃CN by stronger σ-donor ligands (e.g., H₂O, MeOH, DMF) may be caused by prevention of electron transfer from the peroxo group to the metal to give V^IVOO•. Vanadium(V) superoxo complex V^V(O₂^.−) detected by EPR in a solution of VO(O₂) (Pic) (H₂O)₂ in 30% H₂O₂was inert towards alkenes and spin traps.

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VO(O2) (Pic) (H2O)2氧化机理的51V NMR和EPR研究

利用51V核磁共振(NMR)证实了过氧配合物VO(O2) (Pic) (H2O)2 (Pic =吡啶酸)在CH3CN、MeOH和H2O中分别以VO(O2) (Pic) H2O·CH3CN、VO(O2) (Pic) H2O·MeOH和VO(O2) (Pic) (H2O)2的形式存在。为了阐明VO(O2) (Pic) H2O·S族钒过氧配合物对碳氢化合物的反应性质，用EPR研究了它们与自旋阱3,3,5,5-四甲基吡咯烷- n -氧化物(TMPO)的相互作用。只有过氧配合物VO(O2) (Pic) H2O·CH3CN对碳氢化合物和自旋阱有反应。该配合物可以从TMPO中提取β-氢原子(通过该反应VV还原为VIV)。在研究的其他自由基(OH•(HO2•)、RO•(RO2•)和超氧配合物Pd3(OAc)5O2•)中，没有观察到这种氢原子的抽离。后一种物质通过加入双键与TMPO形成自旋加合物。结果表明，双自由基VIVOO•是VO(O2) (Pic) H2O·CH3CN氧化活性粒子。当VO(O2) (Pic) H2O·CH3CN被更强的σ-给体(如H2O, MeOH, DMF)取代后，VO(O2) (Pic) H2O·CH3CN失活可能是由于防止电子从过氧基团转移到金属以获得VIVOO•。钒(V)超氧配合物VV(O2.−)在VO(O2) (Pic) (H2O)2的30% h2o2溶液中被EPR检测到，对烯烃和自旋阱是惰性的。

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来源期刊

分子催化 Chemical Engineering-Catalysis

CiteScore

1.50

自引率

0.00%

发文量

2959

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